Closed-head injuries include injuries to the brain in which the brain impacts the skull, but the skull and dura mater remain intact. Closed-head injuries may be caused by a sudden force to the head, such as the head impacting a headrest during a vehicular accident, or by less forceful collisions between the brain and the skull repeated over a long period time, such as helmet-to-helmet collisions in football. Examples of closed-head injuries include concussions, intracranial hematomas, and cerebral contusions. It is estimated that closed-head injuries account for more than 12 million brain injuries annually in the United States.
One method of assessing the severity of a closed-head injury is the Glasgow Coma Scale. The Glasgow Coma Scale categorizes the severity of a closed-head injury on a scale of three to fifteen based on responses to eye, verbal, and motor tests. Each test is scored on a scale based on a given response; eye responses are assessed on a scale of one to four, verbal responses are assessed on a scale of one to five, and motor responses are assessed on a scale of one to six. The scores are then summed and compared to the Glasgow Coma Scale. If the total score is less than nine, the brain injury is classified as severe. If the score is between nine and twelve (inclusive), the injury is classified as moderate. If the score is greater than twelve, the injury is classified as minor. Other methods for diagnosing a brain or head injury exist as well.